clean unused oil would be okay.

yes to make biodiesel you have filter and treat the used oil to remove the salt and sediment before converting it to biofuel. the other issue with homemade biofuel is not getting the solvent and catalyst ratios exactly right get it wrong you have a fuel that is corrosive, mildly toxic and will disolve the seals in the fuel system. in my state its illeagal to keep the volumes of methanol and cuastic required at domestic premisis and if found the fire service will confiscate it and the equipment.

i know someone that runs his dribble fed injection macdonald diesel on a mix of filtered used cooking oil and kerosene at a 4:1 ratio and it works well but they are a very basic brons fuel system engine so it wont hurt them.

Rome wrote:

I switched to Betty Crocker vegetable oil, if i blow a hose it wont hurt the environment and the used oil is for frying fish.
Just guessing but i think RomeK/G might have been sarcastical. But good info on veggie fuel either way